DIESEL TIMING METER TIMING ADJUSTMENT SPECS

THE SNAP-ON DIESEL TIMING METER, MT480 (KENT-MOORE J-33075), IS A PART OF THE 1982 MODEL ESSENTIAL TOOL PACKAGE. THE MAIN PURPOSE OF THE METER IS TO CHECK DYNAMIC TIMING. (A TIMING/ADJUST IS REQUIRED FOR 1982 MODELS AT 30,000 MILE INTERVALS.) REFER TO THE 1982 SERVICE MANUAL, PAGE 6C5-3, FOR ADJUSTMENT PROCEDURES. THE METER CAN BE USED ON ALL PAST MODEL DIESEL ENGINES. THE METER MONITORS THE COMBUSTION PROCESS TO DETERMINE THE ACTUAL POINT OF IGNITION. SINCE THE ACTUAL POINT OF IGNITION VARIES WITH ALTITUDE AT THE SAME MECHANICAL SETTING, THE TIMING SPECIFICATION IS DIFFERENT AT HIGH ALTITUDE THAN IT IS AT LOW ALTITUDE. THE PROPER SPECIFICATIONS ARE LISTED BELOW: LOW ALTITUDE COUNTIES HIGH ALTITUDE COUNTIES YEAR ENGINE TIMING RPM TIMING RPM 1978 5.7L -4 1/2F 1200 -5 1/2F 1200 1979 5.7L & 4.3L AMT -4 1/2F 1200 -5 1/2F 1200 4.3L SMT -3 1/2F 1200 -4 1/2F 1200 1980 5.7L -4 1/2F 1200 -5 1/2F 1200 1981 5.7L -4F 1200 -5F 1200 1982 5.7L LOW ALTITUDE EMISSIONS PACKAGE -4F 1250 -5F 1250 5.7L HIGH ALTITUDE EMISSIONS PACKAGE -3F 1250 -4F 1250 4.3L LT6 LOW ALTITUDE EMISSION PACKAGE -7F 1300 -8F 1300 4.3L LT6 HIGH ALTITUDE EMISSION PACKAGE -6F 1300 -7F 1300 4.3L LT7 NOT AVAILABLE NOT AVAILABLE CONDITIONS THAT ARE AFFECTED BY DYNAMIC TIMING ARE SMOKE, NOISE, FUEL ECONOMY, STARTING, AND CHUGGLE. HANDLE THE PROBE WITH CARE. DROPPING IT MAY FRACTURE THE QUARTZ. USE SAFETY GLASSES WHENEVER OBSERVING THE LIGHT THROUGH THE PROBE. THERE ARE CERTAIN PROCEDURES THAT MUST BE FOLLOWED TO OBTAIN CORRECT TIMING READINGS: PROCEDURE 1.REVIEW THE PROCEDURE IN THE SERVICE MANUAL, PAGE 6C5-3 BEFORE STARTING. CAUTION: DO NOT USE THE GLOW PLUG PROBE SUPPLIED WITH THE TIMING METER ON ENGINES OTHER THAN THE OLDSMOBILE MANUFACTURED 5.7L V-8 AND 4.3L V-8 OR V-6. WHEN USED ON OTHER ENGINES THIS GLOW PLUG PROBE CAN BE FORCIBLY EXPELLED, POSSIBLY CAUSING PERSONAL INJURY. 2.CORRECT ENGINE CONDITIONS SUCH AS ROUGH IDLE, ENGINE MISS, PLUGGED FUEL FILTERS, OR RESTRICTED FUEL RETURN LINES PRIOR TO TIMING THE ENGINE. 3.DISCONNECT THE EGR. 4.DISCONNECT THE TWO WIRE CONNECTOR TO THE ALTERNATOR. 5.DO NOT OVERTIGHTEN THE GLOW PLUG PROBE. 6.RESET THE ENGINE IDLE SPEED WITH THE TRANSMISSION IN "DRIVE". AFTER RETIMING THE ENGINE, THE MARKS ON THE PUMP FLANGE WILL NORMALLY BE ALIGNED WITHIN .8MM (.030") ON A V-8 AND 1.3MM (.050") ON A V-6. MARKS THAT ARE NOT ALIGNED WITHIN THIS SPECIFICATION MAY INDICATE AN ENGINE MALFUNCTION THAT HAS CAUSED A TIMING SHIFT THAT MUST BE CORRECTED. IF A LARGE CHANGE IN TIMING IS EXPERIENCED, INSTALL THE PROBE IN THE ALTERNATE CYLINDER (NO. 2 ON V-8, NO. 4 ON V-6). TO CONFIRM THE RESULTS OBTAINED IN PREFERRED PROBE LOCATION (NO. 3 ON V-8, NO. 1 ON V-6). ALSO CHECK THE HARMONIC BALANCER TO BE SURE THERE ARE NO NICKS OR GROOVES. IF NICKS OR GROOVES OTHER THAN THE SAW MARK ARE FOUND, REPLACE THE HARMONIC BALANCER. 4.3L V-6 DIESEL ENGINE TIMING SPECIFICATIONS DIESEL ENGINE TIMING SPECIFICATIONS WERE LISTED FOR ALL DIESEL ENGINES EXCEPT THE 4.3L V-6 LT7 ENGINE ON PAGE 18 OF THE DECEMBER SERVICE GUILD. TIMING SPECIFICATIONS FOR THIS ENGINE ARE AS FOLLOWS: LOW ALTITUDE COUNTIES TIMING -5F LOW ALTITUDE COUNTIES RPM 1300 HIGH ALTITUDE COUNTIES TIMING -5F HIGH ALTITUDE COUNTIES RPM 1300 PLEASE NOTE THESE SPECIFICATIONS IN YOUR DECEMBER SERVICE GUILD.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.